1. Field
The present invention relates to uniform resolution image capturing and rendering.
2. Background
An online map service such as Street View by Google Inc. of Mountain View, Calif., allows users to navigate within street-level imagery of certain places for a virtual tour of these places. The images used are panoramic views of street level scenes with information related to the scenes to simulate the experience of virtually walking down a street and exploring the neighborhood.
High resolution cameras are employed to capture the street-level imagery. Typically a camera system comprising multiple cameras is mounted on top of a vehicle that travels along the streets, while the individual cameras capture portions of a panoramic image that are bound by their respective angular fields of view. The panoramic image may be, for example, a 360-degree panorama. Images captured by individual cameras are then stitched together to render the panoramic image. In order to simulate the feeling that a viewer is in the middle of a scene, the panoramic image should be projected along the surface of a cylinder centered around the viewer. Typically, when a two-dimensional rectilinear image of a scene is mapped onto a cylindrical surface, the pixels at the edge of the image within the field of view are viewed at an angle, making the effective width of the pixels at the edge smaller than the effective width of the pixels in the interior of the image. Thus, the viewer sees the image with non-uniform resolution, and the image appears distorted. This is especially true for cameras that employ ultra-wide-angle lenses, known as fish-eye lenses.
This problem may be solved by using individual cameras with narrow fields of view, such that the image-distortion is either not perceptible, or within an acceptable limit. However, this solution calls for an increased number of cameras to capture the entire panorama, and requires a more complicated stitching algorithm.
What is needed is a system and method for tailoring the distortion of the pixels of a two-dimensional rectilinear image, without sacrificing the angular field of view, such that a resultant image projected along the surface of a virtual cylinder appears to have uniform resolution.